Urea Phosphate (UP) - A New Benchmark for Saline-Alkaline Soil Improvement

I. Product Characteristics and Manufacturing Process

Urea Phosphate (UP), also known as urea phosphate fertilizer, is a novel inorganic nitrogen-phosphorus compound produced through the reaction of phosphoric acid and urea at an equimolar ratio. Its chemical formula is CO(NH₂)₂·H₃PO₄. Combining the advantages of both nitrogen and phosphorus nutrition, UP features excellent water solubility, high nutrient purity, low salt content, and chloride-free composition, making it particularly suitable for modern agriculture, saline-alkaline soil reclamation, and precision irrigation systems.

Key Physical and Chemical Properties

• Appearance: Colorless transparent prismatic crystal

• Molecular Formula: CO(NH₂)₂·H₃PO₄

• Molecular Weight: 158.06

• Density: 1.74 g/cm³

• Melting Point: 115-117°C

• Total Nutrient Content: >62%

• Nitrogen (N): 17.7%

• Phosphorus Pentoxide (P₂O₅): 44.9%

• pH (1% solution): approximately 1.89

Due to its acidic nature, Urea Phosphate functions not only as a fertilizer but also as a natural soil acidifying agent capable of improving alkaline soil conditions.

Synthesis Reaction

H₃PO₄ + CO(NH₂)₂ → CO(NH₂)₂·H₃PO₄

Manufacturing Technologies

Commercial production of Urea Phosphate generally follows two routes:

Thermal Phosphoric Acid Process

• High product purity

• Low impurity levels

• Superior product quality

• Higher production costs

Wet-Process Phosphoric Acid Route

• Lower raw material cost

• Large-scale production capability

• Better economic efficiency

• Widely adopted by international manufacturers

In China, both production routes coexist, with high-purity thermal-process Urea Phosphate traditionally dominating the premium market. However, continuous improvements in wet-process production technology have significantly reduced manufacturing costs, making large-scale adoption increasingly feasible.

II. Major Application Areas of Urea Phosphate

Urea Phosphate serves both as a feed additive and a specialty fertilizer, offering broad application potential.

Livestock Feed Applications

In animal nutrition, Urea Phosphate is widely used as a high-quality non-protein nitrogen (NPN) source for ruminants such as cattle and sheep. It can improve feed efficiency, promote animal growth, and enhance production performance. Many commercial ruminant nutritional supplements utilize Urea Phosphate as a key active ingredient.

Agricultural Applications

In agriculture, Urea Phosphate is increasingly recognized as a specialized nitrogen-phosphorus fertilizer for saline-alkaline soil improvement. Its unique ability to acidify the root zone, enhance nutrient availability, reduce nitrogen losses, and maintain compatibility with fertigation systems makes it highly effective in:

• Saline-alkaline soils

• Calcareous soils

• Alkaline soils

• Water-saving irrigation systems

• High-value crop production

Field trials conducted by Chinese agricultural research institutions between 2021 and 2023 demonstrated significant improvements in soil conditions and crop productivity when Urea Phosphate was incorporated into saline-alkaline land management programs.

III. Mechanisms for Saline-Alkaline Soil Improvement

1. Precise Soil pH Regulation

Conventional urea hydrolyzes rapidly after application, often increasing soil pH and aggravating alkalinity-related problems.

In contrast, Urea Phosphate gradually dissociates in the soil and continuously releases acidic components that neutralize excess alkalinity.

Field studies have shown that root-zone soil pH can decrease by approximately 0.9–2.69 units within 28 days of application, significantly improving soil chemical balance and promoting healthier root development.

This effect is particularly valuable for:

• Saline-alkaline soils

• Calcareous soils

• Sodic soils

• High-pH irrigated farmland

Additionally, controlled acidification can help reduce aluminum toxicity in acidic soils, broadening its applicability across diverse agricultural environments.

2. Reduced Ammonia Volatilization and Enhanced Nitrogen Efficiency

Ammonia volatilization is one of the major causes of nitrogen fertilizer loss, especially in alkaline soils where losses may reach 40–50% of applied nitrogen.

Urea Phosphate improves nitrogen use efficiency through two mechanisms:

• Lowering soil pH around fertilizer placement zones

• Slowing the hydrolysis rate of urea

As a result, ammonia emissions are significantly reduced, often by more than 30% compared with conventional nitrogen fertilizers.

Higher nitrogen retention translates into:

• Improved nutrient utilization

• Reduced fertilizer application frequency

• Lower overall fertilization costs

• Enhanced crop nutrient uptake

3. Activation of Secondary and Micronutrients

In saline-alkaline and calcareous soils, nutrients such as calcium, magnesium, zinc, manganese, and iron frequently become unavailable due to precipitation reactions under high-pH conditions.

Traditional phosphate fertilizers may further contribute to nutrient fixation by forming insoluble calcium phosphate compounds.

Urea Phosphate helps overcome these limitations by:

• Releasing hydrogen ions that dissolve nutrient precipitates

• Increasing nutrient solubility

• Enhancing micronutrient availability

• Improving soil structure

This creates a multi-functional effect that combines:

• Phosphorus supply

• Nitrogen supply

• Soil activation

• Improved micronutrient utilization

IV. Agronomic Benefits and Field Adaptability

1. Improved Yield and Crop Quality

Field trials conducted in saline-alkaline cotton-growing regions of Northwestern China have demonstrated notable agronomic benefits.

Compared with conventional fertilization programs, Urea Phosphate applications have been associated with:

• Reduced boll shedding

• Increased boll weight

• Improved crop vigor

• Yield increases of up to 37.2%

The same agronomic principles can benefit grain crops, vegetables, fruit crops, and other high-value agricultural systems.

2. Enhanced Soil Biological Environment

Long-term application of organic manures and intensive cultivation can alter soil microbial populations and increase the risk of soil-borne diseases.

Urea Phosphate has been observed to support beneficial microbial activity by promoting:

• Ammonifying bacteria

• Nitrifying bacteria

• Nitrogen-fixing microorganisms

At the same time, its acidic properties may help suppress certain harmful microbial populations, contributing to healthier soil ecosystems and reduced disease pressure.

3. Excellent Compatibility with Drip Irrigation Systems

Water used in many irrigation districts contains elevated levels of calcium and magnesium, which can cause scale formation and clogging in drip irrigation systems.

The acidic nature of Urea Phosphate helps:

• Improve calcium and magnesium solubility

• Complex metal ions in irrigation water

• Reduce scale formation

• Prevent emitter blockage

• Extend irrigation equipment service life

These characteristics make Urea Phosphate particularly suitable for modern fertigation and water-saving agriculture.

V. Industry Outlook and Future Development

Urea Phosphate is a multifunctional nitrogen-phosphorus fertilizer that integrates soil improvement, nutrient efficiency enhancement, nutrient activation, and irrigation compatibility into a single product.

Compared with conventional compound fertilizers and standard phosphate fertilizers, Urea Phosphate offers:

• Higher nutrient utilization efficiency

• Stronger soil-conditioning effects

• Broader application flexibility

• Chloride-free and low-salt characteristics

• Excellent compatibility with organic fertilizers, micronutrients, and water-soluble fertilizer programs

As continuous wet-process manufacturing technologies further reduce production costs, the economic competitiveness of Urea Phosphate continues to improve.

Driven by global efforts to reclaim saline-alkaline land, improve soil health, enhance fertilizer efficiency, and promote sustainable agriculture, Urea Phosphate is expected to play an increasingly important role in modern crop nutrition programs. Its unique combination of agronomic performance and soil improvement capability positions it as one of the most promising specialty fertilizer products for the future of high-efficiency agriculture.

Urea Phosphate (UP) - A New Benchmark for Saline-Alkaline Soil Improvement